//HJ100
#include<stdio.h>
int main()
{
	int n = 0;
	int an;
	while (scanf("%d", &n) != EOF)
	{
		an = 2 + (n - 1) * 3;
		printf("%d", (2 + an)*n / 2);
	}
	return 0;
}


//HJ76
#include<stdio.h>
int main()
{
	int n = 0;
	while (scanf("%d", &n) != EOF)
	{
		int i = 0;
		for (i = 0; i<n - 1; i++)
		{
			printf("%d+", n*(n - 1) + i * 2 + 1);
		}
		printf("%d", n*(n - 1) + 2 * (n - 1) + 1);
	}
	return 0;
}